The present invention relates to robot control systems and more particularly to the energization and control of brushless DC joint motors employed in such systems.
Better robot performance and more economic robot control manufacture can be achieved with use of a completely digital robot control system as more fully considered in the various cross-referenced patent applications. The digital robot control disclosed in these applications includes digital pulse width modulation (PWM) circuitry employed to control the on time for drive current supplied to the robot joint motors. In W. E. 53,225, the PWM circuitry is fully disclosed and claimed, and it is described in connection with both DC brush type robot joint motors and DC brushless robot joint motors.
Since the disclosed PWM circuitry embodiment is structured to produce output control signals operative to switch power amplifier circuitry employed with DC brush type robot joint motors, a need has existed to adapt the PWM circuitry for operation with DC brushless robot joint motors. Such adaptation requires provision of commutation for the brushless motor windings in addition to basic on/off winding energization control.
Although commutation has been provided by analog circuitry in power amplifiers for brushless DC motors in the prior art, such known commutation schemes have no application to the more advanced digital robot control.
The present invention accordingly is directed to the adaptation of digital PWM circuitry to brushless DC motors in a digital robot control.